Transmission with double-annular gear coplanar gear set

ABSTRACT

A transmission includes a first gear set with a sun gear member rotatable about a first axis of rotation, a carrier member, and a ring gear member radially outward of and concentric with the first sun gear member. A first annular gear meshes with the sun gear member, and a second annular gear meshes with the first annular gear and with the ring gear member. The first annular gear is rotatable about a second axis of rotation and the second annular gear is rotatable about a third axis or rotation.

CROSS-REFERENCE TO RELATED APPLICATION

U.S. Provisional Application No. 61/606,125 filed on Mar. 2, 2012 ishereby incorporated by reference in its entirety.

TECHNICAL FIELD

The present teachings generally include transmissions that have acoplanar gear set.

BACKGROUND

Most passenger vehicles include a powertrain that has an engine, amulti-speed transmission, and a differential or final drive. Themulti-speed transmission increases the overall operating range of thevehicle by permitting the engine to operate through its torque range anumber of times. A primary focus of transmission and engine design isincreasing vehicle fuel efficiency. Generally, an increased number ofspeed ratios provides greater fuel efficiency. However, it ischallenging to package gear sets and selectively engageabletorque-transmitting mechanisms to achieve the desired modes of operationwhile still meeting other applicable dimensional limitations andachieving relatively simple assembly requirements.

SUMMARY

A transmission is provided that has a coplanar gear set with two annulargears. Specifically, the transmission includes a first gear set having asun gear member rotatable about a first axis of rotation. The sun gearmember has a radially outward-facing surface defining outer teeth. Thetransmission has a carrier member and a ring gear member. The ring gearmember is radially outward of and concentric with the sun gear memberand rotatable about the first axis of rotation. The ring gear member hasa radially inward-facing surface defining inner teeth. A first annulargear is supported by the carrier member and has a radially inward-facingsurface defining inner teeth and a radially outward-facing surfacedefining outer teeth. The first annular gear is rotatable about a secondaxis of rotation that rotates about the first axis of rotation. Theinner teeth of the first annular gear mesh with the outer teeth of thesun gear member. A second annular gear is supported by the carriermember and has a radially inward-facing surface defining inner teeth anda radially outward-facing surface defining outer teeth. The secondannular gear is rotatable about a third axis of rotation that rotatesabout the first axis of rotation. The inner teeth of the second annulargear mesh with the outer teeth of the first annular gear and the outerteeth of the second annular gear mesh with the inner teeth of the ringgear member.

By providing the coplanar gear set with another gear set that may or maynot also be a coplanar gear set, axial space savings are achieved.Moreover, a coplanar gear set can achieve a wider gear set ratio rangethan a planetary gear set, has a high contact ratio, and has relativelyquiet operation.

The above features and advantages and other features and advantages ofthe present invention are readily apparent from the following detaileddescription of the best modes for carrying out the invention when takenin connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic cross-sectional illustration of a portion of afirst embodiment of a transmission including a coplanar gear set takenat lines 1-1 in FIG. 2.

FIG. 2 is a schematic cross-sectional illustration of the portion of thetransmission of FIG. 1 taken at lines 2-2 in FIG. 1.

FIG. 3 is a schematic illustration in lever diagram form of thetransmission of FIGS. 1 and 2 including a second gear set.

DETAILED DESCRIPTION

Referring to the drawings, wherein like reference numbers refer to likecomponents throughout the several views, FIGS. 1 and 2 show a portion ofa transmission 10 that includes a first gear set 12 that is a coplanargear set. As used herein, a “coplanar gear set” is a gear set thatincludes an annular gear. As used herein, an “annular gear” is a gearthat is generally cylindrical with radially inward-facing teeth (i.e.,inner teeth) and radially outward-facing teeth (i.e., outer teeth) andhas an axis of rotation that is offset from an axis of rotation of gearswith which it meshes. An annular gear may also be referred to herein asa cluster gear. The annular gear meshes at both its inner and outerteeth with other members of the coplanar gear set.

The first gear set 12 has a sun gear member 16 rotatable about a firstaxis of rotation 18. The sun gear member 16 is mounted on and may beintegrally formed with a center shaft 20. The first gear set 12 has aring gear member 22 that is radially outward of and concentric with thesun gear member 16. The ring gear member 22 has a hub 23 with a centralopening 25 that receives the shaft 20. The ring gear member 22 is thussupported by the shaft 20 and symmetrically positioned about the shaft20 so that the ring gear member 22 is rotatable about the first axis ofrotation 18. The sun gear member 16 has a radially outward-facingsurface 14 defining outer teeth 17. The ring gear member 22 has aradially inward-facing surface 24 with inner teeth 26.

The first gear set 12 has a first annular gear 32 that has a radiallyinward-facing surface 34 with inner teeth 36 and a radiallyoutward-facing surface 38 with outer teeth 40. The first gear set 12also has a carrier member 42. The carrier member 42 has an inner opening43 at which it is rotatably supported by the shaft 20. That is, thefirst carrier member 42 can rotate relative to the shaft 20 and the sungear member 16. The carrier member 42 also has a generally cylindricalfirst hub 44 that is not centered with the first axis of rotation 18.That is, the first hub 44 is an eccentric hub. The first annular gear 32is supported by the hub 44 of the carrier member 42 at a first set ofcluster bearings 46 so that the first annular gear 32 is rotatablerelative to the hub 44. Because the hub 44 is not centered with thefirst axis of rotation, the first annular gear 32 has a second axis ofrotation 48 that is offset from the first axis of rotation 18.Specifically, the first annular gear 32 will rotate around the secondaxis of rotation 48, and as the first annular gear 32 moves the secondaxis of rotation 48 will rotate around the first axis of rotation 18 ina circle with a radius R1 that is equal to the distance by which thesecond axis of rotation 48 is offset from the first axis of rotation 18.

The first gear set 12 has a second annular gear 56 that has a radiallyinward-facing surface 60 with inner teeth 62 and a radiallyoutward-facing surface 64 with outer teeth 66. The carrier member 42also has a generally cylindrical second hub 45 that is not centered withthe first axis of rotation 18. That is, the second hub 45 is aneccentric hub. The second annular gear 56 is supported by the second hub45 of the carrier member 42 at a second set of cluster bearings 58 sothat the second annular gear 56 is rotatable relative to the second hub45. Both the first annular gear 32 and the annular gear 56 are thussupported by a single, common carrier member 42. As is apparent in FIG.2, the first hub 44 extends axially from the second hub 45. Because thesecond hub 45 is not centered with the first axis of rotation 18 or withthe second axis of rotation 48, the second annular gear 56 has a thirdaxis of rotation 68 that is offset from the first axis of rotation 18.Specifically, the second annular gear 56 will rotate around the thirdaxis of rotation 68, and as the second annular gear 56 moves the thirdaxis of rotation 68 will rotate around the first axis of rotation 18 ina circle with a radius R2 that is equal to the distance by which thethird axis of rotation 68 is offset from the first axis of rotation 18.

The inner teeth 36 of the first annular gear 32 mesh with the teeth 17of the sun gear member 16. The outer teeth 40 of the first annular gear32 mesh with the inner teeth 62 of the second annular gear 56. The outerteeth 66 of the second annular gear 56 mesh with the inner teeth 26 ofthe ring gear member 22. The hub 23 of the ring gear member 22 ispositioned so that the sun gear member 16 is between the carrier member42 and the hub 23 and is radially surrounded by the first annular gear32, the second annular gear 56, and the ring gear member 22.

As is apparent in FIG. 2, because the first gear set 12 is a coplanargear set, a radial plane P perpendicular to the first axis of rotation18 and placed through the first gear set 12 intersects the sun gearmember 16, the first annular gear 32, the second annular gear 56, andthe ring gear member 22, so that the meshing of the sun gear member 16with the first annular gear 32, meshing of the first annular gear 32with the second annular gear 56, and meshing of the second annular gear56 with the ring gear member 22 all occur in the single radial plane P.

The first gear set 12 can be used within the transmission 10 along withvarious selectively engageable torque-transmitting mechanisms to providemultiple speed ratios in a relatively compact axial space. That is,because the first gear set 12 is a coplanar gear set, the axial widthoccupied by the first gear set 12 is less than the axial width thatwould be required for two axially-adjacent, simple planetary gear setsthat may be necessary to provide the ratio range available with thefirst gear set 12, potentially reducing weight and increasing fueleconomy. Axial space savings, wide gear set ratio range, high contactratio, and quiet operation can also be achieved.

The speed relationship between the members of the first gear set 12 isas follows:w _(s)=((1/k)*w _(r))+(((k−1)/k)*w _(c)); andk=(ACE)/(BDF);where w_(s) is the rotational speed in revolutions per minute (rpm) ofthe sun gear member 16; w_(r) is the rotational speed in rpm of the ringgear member 22, w_(c) is the rotational speed in rpm of the carriermember 42; A is the number of teeth 17 of the sun gear member 16; B isthe number of inner teeth 36 of the first annular gear 32; C is thenumber of outer teeth 40 of the first annular gear 32; D is the numberof inner teeth 62 of the second annular gear 56, E is the number ofouter teeth 66 of the second annular gear 56, and F is the number ofinner teeth 26 of the first ring gear member 22.

FIG. 3 shows the transmission 10 including the first gear set 12 and asecond gear set 76. The first gear set 12 and the second gear set 76 areillustrated in lever diagram form as will be understood by a person ofordinary skill in the art. Specifically, in a lever diagram, the membersof each gear set are represented as nodes on a lever. Nodes of differentlevers that are interconnected, either continuously or selectively,rotate at the same speed and function as a single node. As used herein,components of gear sets that are interconnected rotate at the samespeed. The distance between each of the nodes on a lever is determinedby the number of teeth on the gear members of the gear set representedby the lever.

The second gear set 76 has a sun gear member 78, a ring gear member 80,and a carrier member 82. A set of planetary gears can mesh both with thering gear member 80 and the sun gear member 78, so that the second gearset 76 is a planetary gear set. Alternatively, an annular gear can meshwith both the sun gear member 78 and the ring gear member 80 so that thesecond gear set 76 is a coplanar gear set that can be stacked with thefirst gear set 12.

The sun gear member 78 of the second gear set 76 is continuouslyinterconnected with the carrier member 42. As used herein, twocomponents are “interconnected” when a rigid interconnection between thetwo components causes the two components to rotate commonly, i.e.,rotate at the same speed as one another. The transmission 10 has aninput member 84 continuously interconnected with the sun gear member 16,and an output member 86 continuously interconnected with the ring gearmember 80 of the second gear set 76.

The transmission 10 has six selectively engageable torque-transmittingmechanisms 90, 92, 94, 96, 98, and 99. The torque-transmittingmechanisms include a first torque-transmitting mechanism 90 that isselectively engageable to interconnect the ring gear member 22 of thefirst gear set 12 to the carrier member 82 of the second gear set 76. Asecond torque-transmitting mechanism 92 is selectively engageable tointerconnect the sun gear member 16 with the carrier member 82. A thirdtorque-transmitting mechanism 94 is selectively engageable tointerconnect the input member 84 with the ring gear member 22.Engagement of the third torque-transmitting mechanism 94 alsointerconnects the sun gear member 16 of the first gear set 12 with thering gear member 22. As is understood by a person skilled in the art,when two members of the first gear set 12 are connected to rotate at thesame speed, the entire first gear set 12 is considered to be “locked” sothat all components of the first gear set 12 rotate at the same speed.When the third torque-transmitting mechanism 94 is engaged, allcomponents of the first gear set 12 rotate at the speed of the inputmember 84.

A fourth torque-transmitting mechanism 96 is selectively engageable toground the ring gear member 22 of the first gear set 12 to a stationarymember 88. As used herein, a “stationary member” is a non-rotatingmember. The stationary member 88 can be a transmission housing. A fifthtorque-transmitting mechanism 98 is selectively engageable to ground thesun gear member 78 of the second gear set 76 to the stationary member88. A sixth torque-transmitting mechanism 99 is selectively engageableto ground the carrier member 82 of the second gear set 76 to thestationary member 88.

The six torque-transmitting mechanisms 90, 92, 94, 96, 98, and 99 areselectively engaged in different combinations to establish fivenumerically different forward speed ratios and a reverse speed ratio ofthe input member 84 to the output member 86. A reverse speed ratio ofthe input member 84 to the output member 86 is established by engagingthe third torque-transmitting mechanism 94 and the sixthtorque-transmitting mechanism 99. A neutral state is established byengaging only the sixth torque-transmitting mechanism 99. A firstforward speed ratio of the input member 84 to the output member 86 isestablished by engaging the first torque-transmitting mechanism 90 andthe sixth torque-transmitting mechanism 99. A second forward speed ratioof the input member 84 to the output member 86 is established byengaging the first torque-transmitting mechanism 90 and the fifthtorque-transmitting mechanism 98. A third forward speed ratio of theinput member 84 to the output member 86 is established by engaging thefirst torque-transmitting mechanism 90 and the secondtorque-transmitting mechanism 92. A fourth forward speed ratio of theinput member 84 to the output member 86 is established by engaging thesecond torque-transmitting mechanism 92 and the fifthtorque-transmitting mechanism 98. A fifth forward speed ratio of theinput member 84 to the output member 86 is established by engaging thesecond torque-transmitting mechanism 92 and the fourthtorque-transmitting mechanism 96.

Transitions between each of the subsequent forward speed ratios aresingle transition shifts. One of the torque-transmitting mechanismsremains engaged during immediate subsequent ratios (i.e., first tosecond forward speed ratio, second to third forward speed ratio, thirdto fourth forward speed ratio, and fourth to fifth forward speed ratio)while the engagement status of one other torque-transmitting mechanismchanges. Additional speed ratios can be established by adding either orboth of one or more additional gear sets and one or more additionaltorque-transmitting mechanisms (i.e., clutches or brakes) to thetransmission 10.

While the best modes for carrying out the invention have been describedin detail, those familiar with the art to which this invention relateswill recognize various alternative designs and embodiments forpracticing the invention within the scope of the appended claims.

The invention claimed is:
 1. A transmission comprising: a first gear sethaving: a sun gear member rotatable about a first axis of rotation;wherein the sun gear member has a radially outward-facing surfacedefining outer teeth; a carrier member; a ring gear member radiallyoutward of and concentric with the sun gear member and rotatable aboutthe first axis of rotation; wherein the ring gear member has a radiallyinward-facing surface defining inner teeth; a first annular gearsupported by the carrier member and having a radially inward-facingsurface defining inner teeth and a radially outward-facing surfacedefining outer teeth; wherein the first annular gear is rotatable abouta second axis of rotation that rotates about the first axis of rotation;wherein the inner teeth of the first annular gear mesh with the outerteeth of the sun gear member; a second annular gear supported by thecarrier member and having a radially inward-facing surface defininginner teeth and a radially outward-facing surface defining outer teeth;wherein the second annular gear is rotatable about a third axis ofrotation that rotates about the first axis of rotation; and wherein theinner teeth of the second annular gear mesh with the outer teeth of thefirst annular gear and the outer teeth of the second annular gear meshwith the inner teeth of the ring gear member.
 2. The transmission ofclaim 1, further comprising: a first set of cluster bearings positionedbetween the first annular gear and the carrier member to permit relativerotation thereof; and a second set of cluster bearings positionedbetween the second annular gear and the carrier member to permitrelative rotation thereof.
 3. The transmission of claim 1, furthercomprising: a shaft extending from the sun gear member; wherein thecarrier member has an opening through which the shaft extends and isrotatably supported by the carrier member to establish the first axis ofrotation; wherein the carrier member has a first eccentric hubsupporting the first annular gear to define the second axis of rotation;and wherein the carrier member has a second eccentric hub supporting thesecond annular gear to define the third axis of rotation.
 4. Thetransmission of claim 3, wherein the first eccentric hub extends axiallyfrom the second eccentric hub.
 5. The transmission of claim 1, furthercomprising: a second gear set having a sun gear member, a ring gearmember, and a carrier member; wherein the sun gear member of the secondgear set is continuously interconnected with the carrier member of thefirst gear set; an input member continuously interconnected with the sungear member of the first gear set; an output member continuouslyinterconnected with the ring gear member of the second gear set; astationary member; six torque-transmitting mechanisms including: a firsttorque-transmitting mechanism selectively engageable to interconnect thering gear member of the first gear set with the carrier member of thesecond gear set; a second torque-transmitting mechanism selectivelyengageable to interconnect the sun gear member of the first gear setwith the carrier member of the second gear set; a thirdtorque-transmitting mechanism selectively engageable to interconnect theinput member with the ring gear member of the first gear set; a fourthtorque-transmitting mechanism selectively engageable to ground the ringgear member of the first gear set to the stationary member; a fifthtorque-transmitting mechanism selectively engageable to ground the sungear member of the second gear set to the stationary member; a sixthtorque-transmitting mechanism selectively engageable to ground thecarrier member of the second gear set to the stationary member; andwherein the six torque-transmitting mechanisms are selectivelyengageable in different combinations to establish five forward speedratios and a reverse speed ratio of the input member to the outputmember.
 6. The transmission of claim 5, wherein shifts between adjacentones of the five forward speed ratios are single transition shifts.
 7. Atransmission comprising: a first gear set having: a sun gear memberrotatable about a first axis of rotation; wherein the sun gear memberhas a radially outward-facing surface defining outer teeth; a carriermember having a first eccentric hub and a second eccentric hub defininga second axis of rotation and a third axis of rotation, respectively; aring gear member radially outward of and concentric with the first sungear member and rotatable about the first axis of rotation; wherein thering gear member has a radially inward-facing surface defining innerteeth; a first annular gear supported by the carrier member on the firsteccentric hub and having a radially inward-facing surface defining innerteeth and a radially outward-facing surface defining outer teeth;wherein the first annular gear is rotatable about the second axis ofrotation; wherein the inner teeth of the first annular gear mesh withthe outer teeth of the sun gear member; a second annular gear supportedby the carrier member on the second eccentric hub and having a radiallyinward-facing surface defining inner teeth and a radially outward-facingsurface defining outer teeth; wherein the second annular gear isrotatable about the third axis of rotation; wherein the inner teeth ofthe second annular gear mesh with the outer teeth of the first annulargear and the outer teeth of the second annular gear mesh with the innerteeth of the ring gear member; and wherein meshing of the sun gearmember with the first annular gear, meshing of the first annular gearwith the second annular gear, and meshing of the second annular gearwith the ring gear member all occur in a plane that is perpendicular tothe first axis of rotation.
 8. The transmission of claim 7, furthercomprising: a first set of cluster bearings positioned between the firstannular gear and the carrier member to permit relative rotation thereof;and a second set of cluster bearings positioned between the secondannular gear and the carrier member to permit relative rotation thereof.9. The transmission of claim 7, wherein the first eccentric hub extendsaxially from the second eccentric hub.
 10. The transmission of claim 7,further comprising: a shaft extending from the sun gear member; whereinthe carrier member has an opening in which the shaft is rotatablysupported to establish the first axis of rotation.
 11. The transmissionof claim 10, wherein the ring gear member has a hub with an opening inwhich the shaft is rotatably supported so that sun gear member ispositioned axially between the carrier member and the hub of the ringgear member.
 12. The transmission of claim 7, further comprising: asecond gear set having a sun gear member, a ring gear member, and acarrier member; wherein the sun gear member of the second gear set iscontinuously interconnected with the carrier member of the first gearset; an input member continuously interconnected with the sun gearmember of the first gear set; an output member continuouslyinterconnected with the ring gear member of the second gear set; astationary member; six torque-transmitting mechanisms including: a firsttorque-transmitting mechanism selectively engageable to interconnect thering gear member of the first gear set with the carrier member of thesecond gear set; a second torque-transmitting mechanism selectivelyengageable to interconnect the sun gear member of the first gear setwith the carrier member of the second gear set; a thirdtorque-transmitting mechanism selectively engageable to interconnect theinput member with the ring gear member of the first gear set; a fourthtorque-transmitting mechanism selectively engageable to ground the ringgear member of the first gear set to the stationary member; a fifthtorque-transmitting mechanism selectively engageable to ground the sungear member of the second gear set to the stationary member; a sixthtorque-transmitting mechanism selectively engageable to ground thecarrier member of the second gear set to the stationary member; andwherein the six torque-transmitting mechanisms are selectivelyengageable in different combinations to establish five forward speedratios and a reverse speed ratio of the input member to the outputmember.
 13. The transmission of claim 12, wherein shifts betweenadjacent ones of the five forward speed ratios are single transitionshifts.
 14. A transmission comprising: a first gear set having: a sungear member rotatable about a first axis of rotation; wherein the sungear member has a radially outward-facing surface defining outer teeth;a carrier member; a ring gear member radially outward of and concentricwith the first sun gear member and rotatable about the first axis ofrotation; wherein the ring gear member has a radially inward-facingsurface defining inner teeth; a first annular gear supported by thecarrier member and having a radially inward-facing surface defininginner teeth and a radially outward-facing surface defining outer teeth;wherein the first annular gear is rotatable about a second axis ofrotation that rotates about the first axis of rotation; wherein theinner teeth of the first annular gear mesh with the outer teeth of thesun gear member; a second annular gear supported by the carrier memberand having a radially inward-facing surface defining inner teeth and aradially outward-facing surface defining outer teeth; wherein the secondannular gear is rotatable about a third axis of rotation that rotatesabout the first axis of rotation; and wherein the inner teeth of thesecond annular gear mesh with the outer teeth of the first annular gearand the outer teeth of the second annular gear mesh with the inner teethof the ring gear member; a first set of cluster bearings positionedbetween the first annular gear and the carrier member to permit relativerotation thereof; a second set of cluster bearings positioned betweenthe second annular gear and the carrier member to permit relativerotation thereof; a second gear set having a ring gear member, a carriermember, and a sun gear member; an input member continuouslyinterconnected with the sun gear member of the first gear set; an outputmember continuously interconnected with the ring gear member of thesecond gear set; a stationary member; six torque-transmitting mechanismsincluding: a first torque-transmitting mechanism selectively engageableto interconnect the ring gear member of the first gear set with thecarrier member of the second gear set; a second torque-transmittingmechanism selectively engageable to interconnect the sun gear member ofthe first gear set with the carrier member of the second gear set; athird torque-transmitting mechanism selectively engageable tointerconnect the input member with the ring gear member of the firstgear set; a fourth torque-transmitting mechanism selectively engageableto ground the ring gear member of the first gear set to the stationarymember; a fifth torque-transmitting mechanism selectively engageable toground the sun gear member of the second gear set to the stationarymember; a sixth torque-transmitting mechanism selectively engageable toground the carrier member of the second gear set to the stationarymember; and wherein the six torque-transmitting mechanisms areselectively engageable in different combinations to establish fiveforward speed ratios and a reverse speed ratio of the input member tothe output member.
 15. The transmission of claim 14, wherein shiftsbetween adjacent ones of the five forward speed ratios are singletransition shifts.